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Comment by clanktron | Hacker News Reader

I love efforts like this. The current state of containers where the dominant mentality is “shove everything possibly needed into a single image and treat it like a black box” isn’t the best imo. Only put what’s necessary and nothing else, you don’t need a whole OS to run a single binary or script.

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> The current state of containers where the dominant mentality is “shove everything possibly needed into a single image and treat it like a black box” isn’t the best imo.

I do something similar for my personal containers.

I have a common Ubuntu base image, that I add a bunch of tools to, which I might need for debugging later and install apt updates to as a part of the build process and remove the apt cache (so instead of changing the base image all the time to a more recent one, I still have an up to date container, at the expense of some additional layers).

Then, on top of that base image I have other specialized images, ones with Apache, some with JDK, some for .NET, Python, Node, Ruby etc., which I can then build my apps upon, while having a few useful tools in the container, as well as a bunch of shared layers that the nodes will be able to reuse.

The only exceptions are images like PostgreSQL, MariaDB, SeaweedFS etc., which I just take from Docker Hub, usually the Bitnami variety: https://bitnami.com/stacks/containers because I almost never need to connect to those or use them as base images, but rather just use them as connected services.

Should enterprises do that? Probably not. It is, however, an immensely pleasant approach to things, that lets me not stress about optimization and just use what works for me.

> Only put what’s necessary

If this were that easy, chroot with PID isolation alone would be quite enough.

It is that easy, at least on distros built for containers. Most stagex based containers are a single binary.

nix can generate images with exactly what's needed and nothing more.

Even for the programs that do something like dlopen("libcrypt.so.3")? Allow me to doubt that.

in nix, you have to be explicit about bringing in something, like libcrypt. otherwise it'll just never be found. so if you can get it to work outside of docker, it's pretty simple to put it in docker with all the things that are needed but nothing else: https://nix.dev/tutorials/nixos/building-and-running-docker-...

https://www.bnikolic.co.uk/blog/python/nix/2023/03/23/nixpyd...

Okay, but how do you find out that this program may dynamically load libcrypt which it doesn't mention in its PT_DYNAMIC for some silly reason or another? Because if you already know that, then you just put "RUN apt install -y openssl" in your Dockerfile which is easy. It's finding out that you need to do that that's hard.

does that mean apt lives in your image? or is it just on the Dev side? nix lives on the Dev side, and your image is not polluted.

the issue of people not documenting their dependencies is not addressed by nix, other than the fact that undocumented dependencies also won't "works on my machine", until it's resolved.

Well no, obviously. Nix has not solved the rice theorem. But you'll have this problem whether you're using BuildKit or Nix. Difference is with Nix the final image only contains your explicitly stated dependencies. I.e. no apt, no Python, no Perl, no cacerts unless you explicitly include them.

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